A new method for obtaining P-S-N curves under the condition of small sample

Abstract

The P- S- N curves are the traditional tool for design against fatigue, which can be transformed into straight lines in the double logarithm coordinate system. There is a widely accepted assumption that the P- S- N curves will intersect at one point if they are extended to the high-stress or low-fatigue life zone. Based on this assumption and from a perspective of geometry, a new method for obtaining P- S- N curves under the condition of small sample is proposed. The proposed method makes it possible to obtain the P- S- N curves by a unified mathematical expression. The validity of the proposed method is verified by the fatigue test data of aluminum alloy 2524-T3. The result indicates that the P- S- N curves obtained by the proposed method with 17 samples agree well with those obtained by the traditional group test method with 59 samples. By comparison, the number of samples and the fatigue test time are reduced by 71.19%, while the average relative error is less than 5%.